Development in light-emitting diode (LED) lighting technology continues to take place at a dramatic pace. With improved brightness, lower energy consumption and longer life spans, the global market for LED lighting has grown exponentially. Further improvements in LED performance (e.g. efficiency, long-term reliability, etc.) is desired. This is particularly true for high power LEDs, which may operate under demanding conditions for long hours.
To improve efficiency, highly reflective substrates are widely used for high performance LED packages and modules (e.g., chip-on-board (COB) LED packages). However, such highly reflective substrates can lead to long-term reliability issues that reduce device life span. For example, silver, which is widely used in high reflective substrates due to its high reflectivity, may migrate and/or be oxidized during operation which can tarnish and/or degrade the substrate. Moreover, the speed of degradation accelerates dramatically at higher temperatures.
In an LED device, one or more LED die may be attached to a highly reflective substrate. During operation, the LED dies generate heat which can raise the temperature of the reflective layer in the vicinity of the die and can accelerate the tarnishing and/or degradation effects noted above. Such effects can lead to reliability problems.
LED device designs that improve performance and long-term reliability are desirable.